Electrowetting cell and method of manufacturing an electrowetting cell

ABSTRACT

The electrowetting cell ( 15 ) comprises an outer wall ( 90 ) and an inner wall ( 80 ), said outer wall ( 90 ) being provided with extensions ( 85,86 ) extending on opposing sides of the inner wall ( 80 ). The cell ( 15 ) is further provided with a membrane ( 45 ) for volume expansion and is sealed through an electroplated layer ( 95 ).

The invention relates to an electrowetting cell comprising a bodysection provided with a substrate and at least one side wall, whichsubstrate and side wall jointly define a cavity containingelectrowetting fluids and further comprising at least one end sectionsecured to the body section.

The invention also relates to a method of manufacturing anelectrowetting cell comprising a body section provided with a substrateand a side wall, which substrate and side wall jointly define a cavitycontaining a first and a second electrowetting fluid.

Electrowetting cells are cells in which light is refracted by a meniscusbetween two immiscible fluids. One of the two fluids is electricallyinsulating and the other is electrically conducting. The shape of themeniscus is variable under the influence of a voltage between twoelectrodes, one of which is connected to the electrically conductingfluid and the other to a surface of the body. Such cells are known andcan for instance be applied as lenses or displays. In the case of theapplication of a cell, there is a light-path through the body section.

Such an electrowetting cell is for instance known from WO-A 03/069380.This patent application discloses a lens in which an inner surface ofthe at least one side wall is covered by a hydrophobic fluid contactlayer. When no voltage is applied, the wettability of the fluid contactlayer with respect to the electrically insulating fluid differs from thewettability of the fluid contact layer with respect to the electricallyconducting fluid. Under influence of the applied voltage a change of thewettability occurs. This leads to a change of a contact angle of themeniscus at a line of contact between the fluid contact layer and thefluids, whereby the shape of the meniscus is adjusted. Hence, the shapeof the meniscus is dependent on the applied voltage.

As the electrowetting cell has optical properties and includes fluids,it is of primary importance for an adequate operation that a completefilling of the cell is achieved and that no fluid can leak out of thecell after closing the cell. The cell disclosed in the prior art doesnot give any solution as to how to achieve such a complete filling andprevent fluid leakage.

It is therefore a first object of the invention to provide anelectrowetting cell of the kind mentioned in the opening paragraph,which can be completely filled and is protected against fluid leakageafter closing of the cell.

It is a second object to provide a method of the kind mentioned in theopening paragraph, with which the complete filling can be achieved in anindustrially viable manner.

The first object is achieved in that the at least one side wall of thebody section comprises an inner wall and an outer wall, a portion ofwhich end section is part of the inner wall, thus securing the endsection and the body section, and which outer wall is provided withextensions extending on a first side and a second side of the inner wallopposed to the first side.

The second object is achieved in a cell with an inner and an outer wall,said outer wall having a first and second extension extending onopposite sides of the inner wall; which method comprises the steps of:

providing an outer wall and a substrate, resulting in the cavity;

filling the cavity with the first and the second electrowetting fluid;

providing the end section in the cavity such that it is immersed in atleast one of the fluids at a desired distance to the substrate, portionsof the substrate and the end section and optionally an intermediatespacer forming the inner wall; and

securing the end section to the body section in that the first extensionof the outer wall is positioned on top of the end section.

The solution of the present invention is a double-walled cell. The outerwall provides stability and adequate sealing, whereas the inner wall isbuilt up from the constituent elements that are assembled consecutively.Due to the consecutive assembly and the double wall, the electrowettingfluids can be provided before the end section. As a result, the endsection can be immersed in the fluid, in practice the fluid with thelowest density. Some fluid will flow to above the end section, but isnevertheless kept within the outer wall. The immersion leads to therequired complete filling. An adequate sealing is then arrived at, inthat the outer wall is present on the opposite sides of the inner wall.The outer wall of the package will then comprise only two majormaterials, which can be attached to each other in a good manner. Asuitable combination is metal and glass.

The substrate could be part of the outer wall, but is preferably aseparate part of which an portion is part of the inner wall. A spacermay be present between the portions of the substrate and the endsection. This is suitable but not necessary. The advantage of suchspacer is that it can be provided with any desired surface coating, suchas the above mentioned fluid contact layer. Advantageously, the spaceris provided with a gap on its bottom side. This allows a reduction ofthe height of the cell.

Several embodiments can be envisaged for the first extension that isprovided on top of the end section. It may for instance be a flexibleextension of the outer wall. It may alternatively be a metal layer thatis positioned through a deposition technique, probably with the help ofa tool exerting pressure.

In a preferred embodiment, the first extension is a clamping body thatis assembled on top of the end section as a separate componentand—simultaneously or consecutively—connected to the outer wall. Thisallows an efficient assembly method. Reliable connection can be realizedin both mechanical and chemical means, such as locking features,additional clamps, adhesive layers and sealing layers. Advantageously,use is made of a joining and protective layer that is grown on saidsurfaces. The grown layer is chemically bonded to the surfaces. It hasthe same coefficient of thermal expansion and it is not sensitive toinelastic and irreversible expansion under the influence of temperature.The grown layer can be grown to a desired thickness, therewithsmoothening out gaps and height differences. Moreover, such a grownlayer is quite inert, particularly if provided with an oxide, which maybe a native oxide. Finally, the grown layer is not sensitive to attackby any of the electrowetting fluids and does not have an open or porousstructure that would allow diffusion of molecules. With such a sealing,particularly together with a substrate and end section of glass, theresulting cell is closed hermetically.

A particularly suitable technique hereto is electroplating. Thistechnique has the advantage that it can be applied at bulk level, byimmersing the complete cell into a bath. Such an immersion of thecomplete cell moreover has the advantage that the grown layer extends onthe complete outer wall and on both extensions on either side of theinner wall. Herewith the clamping character of the outer wall isstrengthened.

In a further embodiment, a first and a second electrode which are incontact with at least one of the electrowetting fluids are defined onopposed sides of the cavity in the substrate and at the end section. Atleast two electrodes are needed in the electrowetting cell so as toapply the voltage needed to set the shape of the meniscus. Suchelectrodes can be applied at the inner walls, on opposite sides of themeniscus. In this embodiment however, the electrodes are present at theend section and on the substrate. This actually allows the use of ametal encapsulation without an insulated connection for one of theelectrodes.

Preferably, the substrate is provided with an aperture, at an end ofwhich said electrode is present. The electrode may be present both on asurface of the substrate facing the meniscus and on an opposite surfacefacing away from the meniscus. The latter modification is preferred, asthere is no need to fill said aperture with metal herein: the fluidfills the aperture. Moreover, the manufacture of this electrode can beintegrated with the provision of metal strips that are used for theattachment of the outer wall to the substrate, and hence provide anadequate sealing.

It is preferred that the package is provided with a volume expansionmember. Such an expansion member is for instance known from JP-A2002/162506. This known package comprises a specific chamber that ispresent adjacent to the substrate, and is separated from the cell with aflexible cover. On increase of the pressure in the cell, the flexiblecover may be deformed or even be stretched out, so as to form a curvedsurface extending into the said chamber. The invention offers thepossibility to locate such a chamber between the inner wall and theouter wall.

A more preferable embodiment of the volume expansion member is aflexible membrane that is part of the end section. In this manner, alarger part of the end section—that is: the part that is present in thelight path—is moved. Hence, a substantial volume increase can becompensated. The flexible membrane is particularly ring-shaped. The endsection is thus divided into an outer edge, a membrane and an innerportion. The standard position of the end section need not to be planarherein. As will be explained with respect to the figures, it isparticularly such that the outer edge is pushed downwards under thepressure of the clamping body. This moreover results in a pressurizedpackage. Although not preferred, it is not excluded that the outer edgeportion of the end section comprises another material than the innerportion.

The membrane is more preferably made of metal. Such a materialwithstands the fluids effectively. It has the additional advantage thatthe membrane can be used as one of the electrodes of the cell. If theconnection between clamping body and outer wall is provided byelectroplating or the like, the membrane will be provided with a metallayer too. A suitable thickness of the membrane layer that hassufficient stability on the one hand and sufficient flexibility on theother hand, is in the order of 5-30 microns, and more preferably between15 and 25 microns. This is also dependent on the material of themembrane. In order to limit the thickness of the membrane, it may beprovided with an insulating coating.

The substrate and the end section are preferably glass plates. Glass isinert against the electrowetting fluids. It can be treated withtechniques such as powder blasting, and metal layers can be attached toit. If desired, one or both glass plates may be provided with coatingsand surface layers, including IR-coatings, UV-absorption coatings,antireflection coatings, but also lenses. Such lenses can be made ofsurface layers with the replica technique. Alignment features may beincluded in such replica made surface layers. This allows a properalignment of the cell with further lenses on the bottom and the topside.

If the cell of the invention is used as a lens, it is suitably assembledwith further lenses to obtain a desired path. It is not excluded thattwo electrowetting lenses are part of the assembly; in fact thisprovides zoom properties. An alternative embodiment is however a stackedelectrowetting lens. This stacked electrowetting lens can be suitablymade with the method of the invention.

In a first embodiment of stacked cell manufacture, the substrate ispresent located in the middle of the stacked cell construction. A firstassembly and filling then takes place on the one side of the substrate,and a second assembly and filling takes place on the opposed second sideafter finalizing the assembly and filling on the first side. Preferablyboth opposite end sections are provided with a flexible membrane forcompensation of volume expansion. The outer wall is provided in thisconstruction with an extension to support the substrate halfway thestacked cell.

In a second embodiment of the stacked cell manufacture, the two cellsare provided within the outer wall one after the other. The end sectionof the first cell may be the substrate of the second cell, but that isnot necessary. Most simply, a spacer is provided instead of the clampingbody. On this spacer, which may well be connected to the outer wall byelectroplating, a further substrate and the further elements of thesecond cell are provided consecutively. Such a construction moreoverallows the electrodes to be located in the substrates and the endsections not needing mutual coupling.

Instead of stacking of several electrowetting cells, the outer wall maybe applied for stacking of one electrowetting cell and further opticaland/or non-optical elements. In addition to separate lenses and filters,it is envisaged that an image sensor is assembled in this manner,separated from the electrowetting lens at a desired distance with anyspacer or the like. Such an integration is most effectively carried outwith an image sensor in which the bond pads are located on a surfaceopposite the optically active surface. Alternatively, the image sensorcan be assembled on top of an interposer substrate, which is providedwith through-holes so as to bring the contacts to a side opposite theoptically active surface. The use of interposer substrates is known perse in the art of semiconductor packaging.

It is an advantage of the method of the invention that it can be carriedout at a wafer-level or a bulk level. The outer wall may be part of aplate, such as a printed circuit board with apertures. It can beseparated into individual packages only after the filling andencapsulating steps. However, even if the manufacture of the cells iscarried out individually, the electroplating steps can occur in a bath,allowing the simultaneous electroplating of a plurality of devices.

The invention is further related to a manufacturing method and a cell ofthe kind mentioned in the opening paragraph, in which a hermetic sealingis provided. This is achieved in that the end section is attached to thebody section with a metal layer that is applied on a surface of both theend section and the joint section. As is explained above, theapplication of a metal layer will lead to a hermetic sealing. A clampingis achieved if the metal layer, or the construction which the metallayer is part of extends on both sides of the cell. A preferredapplication method is electroplating, but other methods such as sol-geldeposition of metal, sputtering or chemical vapor deposition, orcombinations of such deposition methods, are not excluded. The metallayer will suitably be attached to metal parts on the surface of the endsection and on the surface of the body section.

The cell may be used as a lens for use in a camera, in an opticalrecording apparatus or any other optical equipment. The cell may beassembled with further lenses, to obtain an optical path as needed, oreven to obtain a zoom lens. Alternatively, the cell is used as adisplay, in which case only either the substrate or the end sectionneeds to be optically transparent. The cell may be further used as asensor.

These and other aspects of the cell and the method of the invention willbe further elucidated with reference to the figures, in which:

FIG. 1 shows a diagrammatical cross-sectional view of the cell of theinvention, in which only the left part is depicted;

FIGS. 2-7 show diagrammatic cross-sectional views of consecutive stagesin the manufacture of the end section used in the cell;

FIGS. 8-16 show diagrammatic cross-sectional views of consecutive stagesin the method of manufacturing of the cell, in which Figures only theleft part of the cell is depicted.

FIG. 17 shows a diagrammatical cross-sectional view of a secondembodiment of the cell of the invention.

The Figures are diagrammatic and not drawn to scale. The same referencenumbers in different figures refer to like parts.

FIG. 1 shows an embodiment of an electrowetting cell 15 according to theinvention. In this FIG. 1 only a partial cross-sectional view is shown,i.e. only the left part of the cell 15. The cell 15 is however built upsymmetrically, such that the non-shown right part is the mirror of theleft part. The lens includes a fluid chamber, with a first fluid 51 anda second fluid 52, which are non-miscible and contact each other over ameniscus 14. The first fluid 51 is in this example a silicone oil, analkane or another suitable electrically insulating fluid. The secondfluid 52 is in this example water containing a salt solution or anothersuitable electrically conducting fluid. The sides of the chamber areprovided with an electrically insulating layer 8 and a fluid contactlayer 10, for instance parylene.

According to this embodiment, the body section 17 comprises an innerwall 80 and an outer wall 90, and—on the second side 112 of the cell15—the second cover plate 6. The inner wall 80 comprises an electricallyinsulating member 8 that is coated with a fluid contact layer 10. Theinner wall 80 also comprises a portion of the end section 4. This endsection (or first cover plate) 4 comprises a ring-shaped glass member 81that is connected to an inner portion via an expandable joint 45. In apreferred embodiment, this ring-shaped glass member 81 and the innerportion of the end section 4 are manufactured from a single glass plate,as will be explained with reference to FIGS. 2 to 7. The inner wall 80further comprises the end 61 of the second cover plate 6. This secondcover plate 6 is provided with a through hole 62, an electrode 2, and ametallization 63. In an alternative embodiment, the plate 6 may bereplaced by a construction similar or identical to that on the firstside 111 of the cell 15, i.e. a ring-shaped glass member, an expandablejoint and a cover plate.

These three sections of the inner wall 80—the ring-shaped glass member81, the—also ring-shaped—insulating member 8 and the end 61—are clampedbetween a protrusion 85 of the outer wall 90 and a ring-shaped closingmember 86. The closing member 86 is herein a piece of metal, but can beanything with an electrically conducting surface. The outer wall 90comprises an inner core of plastic or other material 92 that is providedwith a metallized surface 91. This metallized surface 91 also bounds themetallization 63 of the second cover plate 6. In this manner, amechanically stable connection is provided.

The inner wall 80 and the outer wall 90 are attached to each other, aswell as to the joint 45 and the end section 4, in that a sealing layer95 is present around it. The sealing layer 95 can be made of a suitablematerial. Polymeric coating of rubber, epoxy or the like, as are knownper se as protective coating may be used. It is however preferred thatthe sealing layer 95 comprises a metal. This allows the provision of apackage that is hermetical and not prone to diffusion of air, water orfluid. A particularly preferred method for the provision of this metalsealing layer 95 is electroplating. This method can be carried out onthree-dimensional surfaces, e.g. in a bath.

FIGS. 2 to 7 show in schematic cross-sectional views consecutive stepsin a method of manufacturing of the substrate 200 with an integratedmembrane 210, to be applied as expandable joint 46. FIG. 2 shows thesubstrate 200, with a first surface 201 and an opposed second surface202. The substrate 200 is in this example a glass plate with a suitablethickness, for instance in the order of 0.1 mm.

FIG. 3 shows the substrate 200, after a photoresist 205 has been appliedon both surfaces 201, 202. Photoresist materials are known per se in theart.

FIG. 4 shows the substrate 200 after patterning and developing thephotoresist 205. The patterning on the first side 201 results in anaperture 214. The patterning on the second side 202 has resulted in thefact that also the surface 215 of the photoresist 205 is given athree-dimensional structure. This surface 215 is in this example in theform of an undulating surface. This surface structure can be provided byforging or another manner of mechanical deformation. Alternatively, useis made of advanced photolithographical techniques. In an even furtherembodiment, use is made of a moulding technique to provide thephotoresist layer 205 in the desired shape. As will be understood, nospecific photoresist material is needed in such a case.

FIG. 5 shows the substrate 200 after a membrane layer 225 has beenapplied. The membrane layer comprises for instance a metal with someelasticity, although any other material is suitable, as long as it iscompatible with the photoresist layer 205. Many metals turn out to havesufficient flexibility if applied as a thin layer. Examples includegold, copper, nickel, aluminum, as well as suitable alloys thereof. Ametal layer may be applied with a suitable deposition technique, such assputtering, chemical vapor deposition and also wet-chemical techniques.In this example, the membrane layer 225 is shown to be patterned, butthat is not necessary.

FIG. 6 shows the substrate 200 after that it has been patterned throughthe patterned photoresist 205 on the first side 201. In the case of aglass plate 200 the technique of power blasting can be appliedadvantageously, which, however, does not exclude any other techniquesuch as etching.

FIG. 7 shows the substrate 200 after the photoresist 205 has beenremoved, and a substrate 200 with an integrated membrane 220 results. Aswill be clear, the substrate 200 may extend in lateral directions. Themembrane 220 may have any suitable shape. Particularly preferred is aring shape. The substrate may contain a plurality of membranes, and besuitable for wafer-level processing in a further step, or be separated.Such a separation step could also be applied before the removal of thephotoresist 205. Although not shown here, it is not excluded that thesubstrate comprises further layers on its first or second side 201, 202.If a semiconductor substrate is used as the substrate 200, semiconductorelements such as diodes and transistors or trench capacitors may bedefined herein.

FIGS. 8 to 16 show diagrammatical cross-sectional views of the method ofmanufacturing of the electrowetting cell 15. Shown here is themanufacture of the embodiment of FIG. 1, but modifications andalternatives are possible within the scope of the present invention.

FIG. 8 shows the first step in the assembly. Herein, a glass substrate 6is provided in a ring-shaped member 90. The ring-shaped member 90 actsas an outer wall, and is provided with an electrically conductingsurface. It is not necessary, though allowed, that the complete surfaceis electrically conducting. The member 90 is provided with an extension85, which is present on a first side 112 of the substrate 6 and is incontact with a adhesion layer 63 of the substrate 6. The adhesion layer63 is here a metal, such as copper. An electrode 2 is present on thesame first side 112 of the substrate 6. This electrode 2 covers anaperture 62 in the substrate 6. The aperture 62 may be filled withelectrically conducting material, but that is not the case in thisexample. The aperture 62 is—contrary to for instance the outer wall90—not ring-shaped, but provided locally only. Instead of glass anothermaterial can be used. In case the cell is not a lens, there is no needfor the substrate to be optically transparent. In order to keep thesubstrate 6 and the outer wall attached, for instance use is made of anadhesive layer.

FIG. 9 shows the result after a second step in the assembly. Herein, thesubstrate 6 and the outer wall 90 are connected to each other with ametal layer 91. This metal layer 91 is suitably provided byelectroplating in a bath. The metal layer 91 extends around the outerwall 90, and is connected to the adhesion layer 63 of the substrate. Theconnection is present not only on the first side 112 of the substrate,but also on a side face 115. Shown here, but not in further figures isthe fact that the electrode 2 will be provided with an electroplatedlayer as well. The position of this electrode 2 is chosen such that nobridge is formed between the electrode and the outer wall. An insulatingcoating may be provided at the electrode 2 in order to prevent thethickening thereof.

FIG. 10 shows the result after an electrically conducting fluid 52 hasbeen provided in the outer wall 90 and on the second side 113 of thesubstrate 6. In this example the fluid 52 is an aqueous salt solution.Alcohols and the like may be used as additional solvents. The fluidextends into the aperture 62, thereby making contact with the electrode2. The electrode 2 acts at the same time as a closure of the cell.

FIG. 11 shows the result after the provision of the electricallyinsulating fluid 51. This is an oil, for instance an alkane or a siliconoil. In view of its lower density, it is provided after the electricallyconducting fluid 51. The shapes of the meniscus shown and the adhesionto the second side 113 of the substrate 6 are purely diagrammatical anddo not necessarily correspond to any physical effect.

FIG. 12 shows the result after the insertion of a spacer 8. This is inthis case a ring-shaped electrically insulating member 8 that isprovided with a fluid contact layer 10 of parylene. The spacer 8 has asurface 9 that may have a modified surface structure or layer for properadhesion to the electroplated layer 91 of the outer wall 90. Thissurface structure or layer can be of any chemical kind, but alsomechanical, such as a locking feature. Additionally, the spacer 8 isprovided with a gap 64. This gap 64 has as a first advantage that theelectrode 2 can be provided below this spacer 8. Hence, the electrode 2is located outside the light path, which reduces the diameter of thecell. A second advantage of the gap is a modification of the angle ofthe meniscus 14 between the electrically conducting fluid 52 and theelectrically insulating fluid 51. As a result, the minimum thickness ofthe cell is reduced. Together with an outer edge 61 of the substrate thespacer forms part of the inner wall.

FIG. 13 shows the cell 15 after a sixth manufacturing step. This stepinvolves the assembly of the end section 4. The end section 4 includesan inner portion, a membrane 45 and an outer portion 81. A pressure tool70 is provided on a first side 111 of the end section 4. Preferably, theend section 4 is provided with a layer of the electrically insulatingfluid on its second side 114 before the actual assembly. This ensuresthat no air bubbles will be formed during the assembly. The end section4 is immersed in the fluid 51 during the assembly. As a result thereof,a surplus layer 55 of the fluid is formed on the first side of the endsection. The electrically insulating fluid 51 is able to flow from thesecond side 114 to the first side 111 of the end section 4, as a narrowchannel is left between the outer portion 81 and the outer wall 90.

FIG. 14 shows the cell 15 after the outer portion 81 of the end section4 has been secured to the body section. This body section comprises infact both the spacer 8 and the outer wall 90. This is carried out byinsertion of a clamping body 86. This body clamps and/or puts the outerportion 81 downwards to the spacer 8. As a result the membrane 45 is putin a slightly bent position. The clamping body has a surface that is incontact with the electroplated surface layer 91 of the outer wall 90. Itis preferably provided with one or more locking features. If desired, itmay be designed to extend into the channel 89 between the outer portion81 and the outer wall 90. In this operation, the inner wall 80 isformed, constituted by the adhesive layer 63, the outer portion 61 ofthe substrate 6, the spacer 8, the outer portion 81 of the end section 4and the clamping body 86.

FIG. 15 shows the cell 15 after removal of the tool 70 and the surplus55 of the electrically insulating fluid 51. The removing step isfollowed by a cleaning step, so that the surfaces of the clamping body86 and the membrane 45 are sufficiently clean for subsequent steps.

FIG. 16 shows the cell 15 after the last important step in themanufacture. In this step, the connection between the clamping body 86and the outer wall 90 is strengthened by the provision of a sealinglayer 95. The sealing layer 95 is preferably provided by electroplatingin a suitable bath. Alternatively, it may be any other protective layerknown per se in the art, such as an epoxy-based layer. The sealing layer95 extends in this example to the membrane 45 but this is not essential.Preferably, the sealing layer 95 is provided in a suitable thickness soas to fill any comers and provide a smoothened outer surface. Thesealing layer 95 extends in this example from the first side 111 of theend section to the first side 112 of the substrate. This isadvantageous, in that it therewith has a clamping character as well, andunifies the outer wall 90 with its extensions 85, 86.

FIG. 17 shows a diagrammatical, cross-sectional view of a secondembodiment of the cell of the invention. Not shown in this embodimentare any electroplated sealing layers that cover the extension 85 of theouter wall 80. In this embodiment, the core 92 of the outer wall is ametallic tray, which inherently comprises the protrusion 85. The secondcover plate 6 with the through-hole 62, the body member 8 and the firstcover plate 4 is herein assembled in the manner described with referenceto FIGS. 8 to 16. The body member 8 will generally operate as one of theelectrodes, and it is for instance connected to the tray 92, which actsas a contact.

The first cover plate 4 is herein a continuous plate that is chosen tobe sufficiently thin so as to be bendable under stress. In this example,use is made of a plate of glass. There is a cavity 41 between the bodymember 8 and the first cover plate 4. Under expansion of at least one ofthe fluids 51,52—particularly at a rise in temperature—the first coverplate 4 will bend so as to enlarge the volume in the cell. Undershrinkage of at least one of the fluids 51,52 the first cover plate willbend so as to diminish the volume in the cell. Since the electricallyinsulating fluid 51 is preferably an oil and has a larger coefficient ofthermal expansion than the aqueous second fluid 52, it is preferable forthe bendable first cover plate 4 to be present on the side of theelectrically insulating fluid 51.

Although not shown here, very good results have been obtained with theelectroplated sealing layer. It is not excluded that this electroplatedsealing layer is also applicable in other configurations of fluidcontaining cells, and that not for all applications a cell with both aninner wall 80 and an outer wall 90 and an extension 85,86 is needed. Itis further understood, that the extensions 85, 86 of the outer wall 80extending on the first and second side 111, 112 are not separateelements, but either protrusions to parts or connections grown ordeposited. Particularly, an electroplated connection may be effective assuch an extension 86.

1. An electrowetting cell comprising a body section provided with asubstrate and at least one side wall, which substrate and side walljointly define a cavity containing electrowetting fluids and furthercomprising at least one end section secured to the body section, whereinthe at least one side wall of the body section comprises an inner walland an outer wall, a portion of which end section is part of the innerwall, thus securing the end section and the body section, and whichouter wall is provided with extensions extending on a first side and asecond side of the inner wall opposed to the first side.
 2. Anelectrowetting cell as claimed in claim 1, wherein the inner wallcomprises a portion of the substrate.
 3. An electrowetting cell asclaimed in claim 2, wherein the inner wall further comprises a spacer ofan electrically insulating material between said portion of thesubstrate and said portion of the end section.
 4. An electrowetting cellas claimed in claim 1, wherein the extension of the outer wall extendingon the first side of the inner wall is a clamping body that is attachedto the outer wall.
 5. An electrowetting cell as claimed in claim 4,wherein the clamping body is attached to the outer wall by means of ametal layer that is grown on the extension and on the outer wall.
 6. Anelectrowetting cell as claimed in claim 1, wherein a first and a secondelectrode which are in contact with at least one of the electrowettingfluids are defined on opposed sides of the cavity in the substrate andat the end section.
 7. An electrowetting cell as claimed in claim 6,wherein the substrate is provided with an aperture, at an end of whichsaid electrode is present.
 8. An electrowetting cell as claimed in claim1, wherein the end section comprises a flexible membrane allowing forvolume expansion of the closed cavity.
 9. An electrowetting cell asclaimed in claim 2, wherein the extension on the second side of theinner wall is attached to the substrate through a metal layer that isgrown on both sides.
 10. An electrowetting cell comprising a bodysection provided with a substrate and at least one side wall, whichsubstrate and side wall jointly define a cavity containingelectrowetting fluids, and further comprising at least one end sectionsecured to the body section, wherein the end section is attached to thebody section with a metal layer that is applied on a surface of both theend section and the joint section.
 11. A method of manufacturing anelectrowetting cell comprising a body section provided with a substrateand a side wall having an inner wall and an outer wall, said outer wallbeing provided with a first and a second extension extending on opposedsides of the inner wall, which substrate and side wall jointly define acavity containing a first and a second electrowetting fluid, whichmethod comprises the steps of: providing an outer wall and a substrate,resulting in the cavity; filling the cavity with the first and thesecond electrowetting fluid; providing the end section in the cavitysuch that it is immersed in at least one of the fluids at a desireddistance to the substrate, portions of the substrate and the end sectionand optionally an intermediate spacer forming the inner wall; securingthe end section to the body section in that the first extension of theouter wall is positioned on top of the end section.
 12. A method asclaimed in claim 11, wherein the extension is a separate clamping bodythat is connected to the outer wall only after having been positioned onthe end section.
 13. A method as claimed in claim 12, wherein theclamping body and the outer wall are connected with a metal layer grownon their surfaces.
 14. An image capturing device or an image sensorincorporating an electrowetting cell as claimed in claim
 1. 15. Anoptical scanning device comprising an electrowetting cell as claimed inclaim
 1. 16. A display device incorporating an electrowetting cell asclaimed in claim 1.